1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * IPv6 fragment reassembly
4 * Linux INET6 implementation
5 *
6 * Authors:
7 * Pedro Roque <roque@di.fc.ul.pt>
8 *
9 * Based on: net/ipv4/ip_fragment.c
10 */
11
12/*
13 * Fixes:
14 * Andi Kleen Make it work with multiple hosts.
15 * More RFC compliance.
16 *
17 * Horst von Brand Add missing #include <linux/string.h>
18 * Alexey Kuznetsov SMP races, threading, cleanup.
19 * Patrick McHardy LRU queue of frag heads for evictor.
20 * Mitsuru KANDA @USAGI Register inet6_protocol{}.
21 * David Stevens and
22 * YOSHIFUJI,H. @USAGI Always remove fragment header to
23 * calculate ICV correctly.
24 */
25
26#define pr_fmt(fmt) "IPv6: " fmt
27
28#include <linux/errno.h>
29#include <linux/types.h>
30#include <linux/string.h>
31#include <linux/socket.h>
32#include <linux/sockios.h>
33#include <linux/jiffies.h>
34#include <linux/net.h>
35#include <linux/list.h>
36#include <linux/netdevice.h>
37#include <linux/in6.h>
38#include <linux/ipv6.h>
39#include <linux/icmpv6.h>
40#include <linux/random.h>
41#include <linux/jhash.h>
42#include <linux/skbuff.h>
43#include <linux/slab.h>
44#include <linux/export.h>
45#include <linux/tcp.h>
46#include <linux/udp.h>
47
48#include <net/sock.h>
49#include <net/snmp.h>
50
51#include <net/ipv6.h>
52#include <net/ip6_route.h>
53#include <net/protocol.h>
54#include <net/transp_v6.h>
55#include <net/rawv6.h>
56#include <net/ndisc.h>
57#include <net/addrconf.h>
58#include <net/ipv6_frag.h>
59#include <net/inet_ecn.h>
60
61static const char ip6_frag_cache_name[] = "ip6-frags";
62
63static u8 ip6_frag_ecn(const struct ipv6hdr *ipv6h)
64{
65 return 1 << (ipv6_get_dsfield(ipv6h) & INET_ECN_MASK);
66}
67
68static struct inet_frags ip6_frags;
69
70static int ip6_frag_reasm(struct frag_queue *fq, struct sk_buff *skb,
71 struct sk_buff *prev_tail, struct net_device *dev,
72 int *refs);
73
74static void ip6_frag_expire(struct timer_list *t)
75{
76 struct inet_frag_queue *frag = timer_container_of(frag, t, timer);
77 struct frag_queue *fq;
78
79 fq = container_of(frag, struct frag_queue, q);
80
81 ip6frag_expire_frag_queue(net: fq->q.fqdir->net, fq);
82}
83
84static struct frag_queue *
85fq_find(struct net *net, __be32 id, const struct ipv6hdr *hdr, int iif)
86{
87 struct frag_v6_compare_key key = {
88 .id = id,
89 .saddr = hdr->saddr,
90 .daddr = hdr->daddr,
91 .user = IP6_DEFRAG_LOCAL_DELIVER,
92 .iif = iif,
93 };
94 struct inet_frag_queue *q;
95
96 if (!(ipv6_addr_type(addr: &hdr->daddr) & (IPV6_ADDR_MULTICAST |
97 IPV6_ADDR_LINKLOCAL)))
98 key.iif = 0;
99
100 q = inet_frag_find(fqdir: net->ipv6.fqdir, key: &key);
101 if (!q)
102 return NULL;
103
104 return container_of(q, struct frag_queue, q);
105}
106
107static int ip6_frag_queue(struct net *net,
108 struct frag_queue *fq, struct sk_buff *skb,
109 struct frag_hdr *fhdr, int nhoff,
110 u32 *prob_offset, int *refs)
111{
112 int offset, end, fragsize;
113 struct sk_buff *prev_tail;
114 struct net_device *dev;
115 int err = -ENOENT;
116 SKB_DR(reason);
117 u8 ecn;
118
119 /* If reassembly is already done, @skb must be a duplicate frag. */
120 if (fq->q.flags & INET_FRAG_COMPLETE) {
121 SKB_DR_SET(reason, DUP_FRAG);
122 goto err;
123 }
124
125 err = -EINVAL;
126 offset = ntohs(fhdr->frag_off) & ~0x7;
127 end = offset + (ntohs(ipv6_hdr(skb)->payload_len) -
128 ((u8 *)(fhdr + 1) - (u8 *)(ipv6_hdr(skb) + 1)));
129
130 if ((unsigned int)end > IPV6_MAXPLEN) {
131 *prob_offset = (u8 *)&fhdr->frag_off - skb_network_header(skb);
132 /* note that if prob_offset is set, the skb is freed elsewhere,
133 * we do not free it here.
134 */
135 return -1;
136 }
137
138 ecn = ip6_frag_ecn(ipv6h: ipv6_hdr(skb));
139
140 if (skb->ip_summed == CHECKSUM_COMPLETE) {
141 const unsigned char *nh = skb_network_header(skb);
142 skb->csum = csum_sub(csum: skb->csum,
143 addend: csum_partial(buff: nh, len: (u8 *)(fhdr + 1) - nh,
144 sum: 0));
145 }
146
147 /* Is this the final fragment? */
148 if (!(fhdr->frag_off & htons(IP6_MF))) {
149 /* If we already have some bits beyond end
150 * or have different end, the segment is corrupted.
151 */
152 if (end < fq->q.len ||
153 ((fq->q.flags & INET_FRAG_LAST_IN) && end != fq->q.len))
154 goto discard_fq;
155 fq->q.flags |= INET_FRAG_LAST_IN;
156 fq->q.len = end;
157 } else {
158 /* Check if the fragment is rounded to 8 bytes.
159 * Required by the RFC.
160 */
161 if (end & 0x7) {
162 /* RFC2460 says always send parameter problem in
163 * this case. -DaveM
164 */
165 *prob_offset = offsetof(struct ipv6hdr, payload_len);
166 return -1;
167 }
168 if (end > fq->q.len) {
169 /* Some bits beyond end -> corruption. */
170 if (fq->q.flags & INET_FRAG_LAST_IN)
171 goto discard_fq;
172 fq->q.len = end;
173 }
174 }
175
176 if (end == offset)
177 goto discard_fq;
178
179 err = -ENOMEM;
180 /* Point into the IP datagram 'data' part. */
181 if (!pskb_pull(skb, len: (u8 *) (fhdr + 1) - skb->data))
182 goto discard_fq;
183
184 err = pskb_trim_rcsum(skb, len: end - offset);
185 if (err)
186 goto discard_fq;
187
188 /* Note : skb->rbnode and skb->dev share the same location. */
189 dev = skb->dev;
190 /* Makes sure compiler wont do silly aliasing games */
191 barrier();
192
193 prev_tail = fq->q.fragments_tail;
194 err = inet_frag_queue_insert(q: &fq->q, skb, offset, end);
195 if (err)
196 goto insert_error;
197
198 if (dev)
199 fq->iif = dev->ifindex;
200
201 fq->q.stamp = skb->tstamp;
202 fq->q.tstamp_type = skb->tstamp_type;
203 fq->q.meat += skb->len;
204 fq->ecn |= ecn;
205 add_frag_mem_limit(fqdir: fq->q.fqdir, val: skb->truesize);
206
207 fragsize = -skb_network_offset(skb) + skb->len;
208 if (fragsize > fq->q.max_size)
209 fq->q.max_size = fragsize;
210
211 /* The first fragment.
212 * nhoffset is obtained from the first fragment, of course.
213 */
214 if (offset == 0) {
215 fq->nhoffset = nhoff;
216 fq->q.flags |= INET_FRAG_FIRST_IN;
217 }
218
219 if (fq->q.flags == (INET_FRAG_FIRST_IN | INET_FRAG_LAST_IN) &&
220 fq->q.meat == fq->q.len) {
221 unsigned long orefdst = skb->_skb_refdst;
222
223 skb->_skb_refdst = 0UL;
224 err = ip6_frag_reasm(fq, skb, prev_tail, dev, refs);
225 skb->_skb_refdst = orefdst;
226 return err;
227 }
228
229 skb_dst_drop(skb);
230 return -EINPROGRESS;
231
232insert_error:
233 if (err == IPFRAG_DUP) {
234 SKB_DR_SET(reason, DUP_FRAG);
235 err = -EINVAL;
236 goto err;
237 }
238 err = -EINVAL;
239 __IP6_INC_STATS(net, ip6_dst_idev(skb_dst(skb)),
240 IPSTATS_MIB_REASM_OVERLAPS);
241discard_fq:
242 inet_frag_kill(q: &fq->q, refs);
243 __IP6_INC_STATS(net, ip6_dst_idev(skb_dst(skb)),
244 IPSTATS_MIB_REASMFAILS);
245err:
246 kfree_skb_reason(skb, reason);
247 return err;
248}
249
250/*
251 * Check if this packet is complete.
252 *
253 * It is called with locked fq, and caller must check that
254 * queue is eligible for reassembly i.e. it is not COMPLETE,
255 * the last and the first frames arrived and all the bits are here.
256 */
257static int ip6_frag_reasm(struct frag_queue *fq, struct sk_buff *skb,
258 struct sk_buff *prev_tail, struct net_device *dev,
259 int *refs)
260{
261 struct net *net = fq->q.fqdir->net;
262 unsigned int nhoff;
263 void *reasm_data;
264 int payload_len;
265 u8 ecn;
266
267 inet_frag_kill(q: &fq->q, refs);
268
269 ecn = ip_frag_ecn_table[fq->ecn];
270 if (unlikely(ecn == 0xff))
271 goto out_fail;
272
273 reasm_data = inet_frag_reasm_prepare(q: &fq->q, skb, parent: prev_tail);
274 if (!reasm_data)
275 goto out_oom;
276
277 payload_len = -skb_network_offset(skb) -
278 sizeof(struct ipv6hdr) + fq->q.len -
279 sizeof(struct frag_hdr);
280 if (payload_len > IPV6_MAXPLEN)
281 goto out_oversize;
282
283 /* We have to remove fragment header from datagram and to relocate
284 * header in order to calculate ICV correctly. */
285 nhoff = fq->nhoffset;
286 skb_network_header(skb)[nhoff] = skb_transport_header(skb)[0];
287 memmove(dest: skb->head + sizeof(struct frag_hdr), src: skb->head,
288 count: (skb->data - skb->head) - sizeof(struct frag_hdr));
289 if (skb_mac_header_was_set(skb))
290 skb->mac_header += sizeof(struct frag_hdr);
291 skb->network_header += sizeof(struct frag_hdr);
292
293 skb_reset_transport_header(skb);
294
295 inet_frag_reasm_finish(q: &fq->q, head: skb, reasm_data, try_coalesce: true);
296
297 skb->dev = dev;
298 ipv6_hdr(skb)->payload_len = htons(payload_len);
299 ipv6_change_dsfield(ipv6h: ipv6_hdr(skb), mask: 0xff, value: ecn);
300 IP6CB(skb)->nhoff = nhoff;
301 IP6CB(skb)->flags |= IP6SKB_FRAGMENTED;
302 IP6CB(skb)->frag_max_size = fq->q.max_size;
303
304 /* Yes, and fold redundant checksum back. 8) */
305 skb_postpush_rcsum(skb, start: skb_network_header(skb),
306 len: skb_network_header_len(skb));
307
308 __IP6_INC_STATS(net, __in6_dev_stats_get(dev, skb), IPSTATS_MIB_REASMOKS);
309 fq->q.rb_fragments = RB_ROOT;
310 fq->q.fragments_tail = NULL;
311 fq->q.last_run_head = NULL;
312 return 1;
313
314out_oversize:
315 net_dbg_ratelimited("ip6_frag_reasm: payload len = %d\n", payload_len);
316 goto out_fail;
317out_oom:
318 net_dbg_ratelimited("ip6_frag_reasm: no memory for reassembly\n");
319out_fail:
320 __IP6_INC_STATS(net, __in6_dev_stats_get(dev, skb), IPSTATS_MIB_REASMFAILS);
321 inet_frag_kill(q: &fq->q, refs);
322 return -1;
323}
324
325static int ipv6_frag_rcv(struct sk_buff *skb)
326{
327 const struct ipv6hdr *hdr = ipv6_hdr(skb);
328 struct net *net = skb_dst_dev_net(skb);
329 struct frag_hdr *fhdr;
330 struct frag_queue *fq;
331 u8 nexthdr;
332 int iif;
333
334 if (IP6CB(skb)->flags & IP6SKB_FRAGMENTED)
335 goto fail_hdr;
336
337 __IP6_INC_STATS(net, ip6_dst_idev(skb_dst(skb)), IPSTATS_MIB_REASMREQDS);
338
339 /* Jumbo payload inhibits frag. header */
340 if (hdr->payload_len == 0)
341 goto fail_hdr;
342
343 if (!pskb_may_pull(skb, len: (skb_transport_offset(skb) +
344 sizeof(struct frag_hdr))))
345 goto fail_hdr;
346
347 hdr = ipv6_hdr(skb);
348 fhdr = (struct frag_hdr *)skb_transport_header(skb);
349
350 if (!(fhdr->frag_off & htons(IP6_OFFSET | IP6_MF))) {
351 /* It is not a fragmented frame */
352 skb->transport_header += sizeof(struct frag_hdr);
353 __IP6_INC_STATS(net,
354 ip6_dst_idev(skb_dst(skb)), IPSTATS_MIB_REASMOKS);
355
356 IP6CB(skb)->nhoff = (u8 *)fhdr - skb_network_header(skb);
357 IP6CB(skb)->flags |= IP6SKB_FRAGMENTED;
358 IP6CB(skb)->frag_max_size = ntohs(hdr->payload_len) +
359 sizeof(struct ipv6hdr);
360 return 1;
361 }
362
363 /* RFC 8200, Section 4.5 Fragment Header:
364 * If the first fragment does not include all headers through an
365 * Upper-Layer header, then that fragment should be discarded and
366 * an ICMP Parameter Problem, Code 3, message should be sent to
367 * the source of the fragment, with the Pointer field set to zero.
368 */
369 nexthdr = hdr->nexthdr;
370 if (ipv6frag_thdr_truncated(skb, start: skb_network_offset(skb) + sizeof(struct ipv6hdr), nexthdrp: &nexthdr)) {
371 __IP6_INC_STATS(net, __in6_dev_get_safely(skb->dev),
372 IPSTATS_MIB_INHDRERRORS);
373 icmpv6_param_prob(skb, ICMPV6_HDR_INCOMP, pos: 0);
374 return -1;
375 }
376
377 iif = skb->dev ? skb->dev->ifindex : 0;
378 rcu_read_lock();
379 fq = fq_find(net, id: fhdr->identification, hdr, iif);
380 if (fq) {
381 u32 prob_offset = 0;
382 int ret, refs = 0;
383
384 spin_lock(lock: &fq->q.lock);
385
386 fq->iif = iif;
387 ret = ip6_frag_queue(net, fq, skb, fhdr, IP6CB(skb)->nhoff,
388 prob_offset: &prob_offset, refs: &refs);
389
390 spin_unlock(lock: &fq->q.lock);
391 rcu_read_unlock();
392 inet_frag_putn(q: &fq->q, refs);
393 if (prob_offset) {
394 __IP6_INC_STATS(net, __in6_dev_get_safely(skb->dev),
395 IPSTATS_MIB_INHDRERRORS);
396 /* icmpv6_param_prob() calls kfree_skb(skb) */
397 icmpv6_param_prob(skb, ICMPV6_HDR_FIELD, pos: prob_offset);
398 }
399 return ret;
400 }
401 rcu_read_unlock();
402
403 __IP6_INC_STATS(net, ip6_dst_idev(skb_dst(skb)), IPSTATS_MIB_REASMFAILS);
404 kfree_skb(skb);
405 return -1;
406
407fail_hdr:
408 __IP6_INC_STATS(net, __in6_dev_get_safely(skb->dev),
409 IPSTATS_MIB_INHDRERRORS);
410 icmpv6_param_prob(skb, ICMPV6_HDR_FIELD, pos: skb_network_header_len(skb));
411 return -1;
412}
413
414static const struct inet6_protocol frag_protocol = {
415 .handler = ipv6_frag_rcv,
416 .flags = INET6_PROTO_NOPOLICY,
417};
418
419#ifdef CONFIG_SYSCTL
420
421static struct ctl_table ip6_frags_ns_ctl_table[] = {
422 {
423 .procname = "ip6frag_high_thresh",
424 .maxlen = sizeof(unsigned long),
425 .mode = 0644,
426 .proc_handler = proc_doulongvec_minmax,
427 },
428 {
429 .procname = "ip6frag_low_thresh",
430 .maxlen = sizeof(unsigned long),
431 .mode = 0644,
432 .proc_handler = proc_doulongvec_minmax,
433 },
434 {
435 .procname = "ip6frag_time",
436 .maxlen = sizeof(int),
437 .mode = 0644,
438 .proc_handler = proc_dointvec_jiffies,
439 },
440};
441
442/* secret interval has been deprecated */
443static int ip6_frags_secret_interval_unused;
444static struct ctl_table ip6_frags_ctl_table[] = {
445 {
446 .procname = "ip6frag_secret_interval",
447 .data = &ip6_frags_secret_interval_unused,
448 .maxlen = sizeof(int),
449 .mode = 0644,
450 .proc_handler = proc_dointvec_jiffies,
451 },
452};
453
454static int __net_init ip6_frags_ns_sysctl_register(struct net *net)
455{
456 struct ctl_table *table;
457 struct ctl_table_header *hdr;
458
459 table = ip6_frags_ns_ctl_table;
460 if (!net_eq(net1: net, net2: &init_net)) {
461 table = kmemdup(table, sizeof(ip6_frags_ns_ctl_table), GFP_KERNEL);
462 if (!table)
463 goto err_alloc;
464
465 }
466 table[0].data = &net->ipv6.fqdir->high_thresh;
467 table[0].extra1 = &net->ipv6.fqdir->low_thresh;
468 table[1].data = &net->ipv6.fqdir->low_thresh;
469 table[1].extra2 = &net->ipv6.fqdir->high_thresh;
470 table[2].data = &net->ipv6.fqdir->timeout;
471
472 hdr = register_net_sysctl_sz(net, path: "net/ipv6", table,
473 ARRAY_SIZE(ip6_frags_ns_ctl_table));
474 if (!hdr)
475 goto err_reg;
476
477 net->ipv6.sysctl.frags_hdr = hdr;
478 return 0;
479
480err_reg:
481 if (!net_eq(net1: net, net2: &init_net))
482 kfree(objp: table);
483err_alloc:
484 return -ENOMEM;
485}
486
487static void __net_exit ip6_frags_ns_sysctl_unregister(struct net *net)
488{
489 const struct ctl_table *table;
490
491 table = net->ipv6.sysctl.frags_hdr->ctl_table_arg;
492 unregister_net_sysctl_table(header: net->ipv6.sysctl.frags_hdr);
493 if (!net_eq(net1: net, net2: &init_net))
494 kfree(objp: table);
495}
496
497static struct ctl_table_header *ip6_ctl_header;
498
499static int ip6_frags_sysctl_register(void)
500{
501 ip6_ctl_header = register_net_sysctl(&init_net, "net/ipv6",
502 ip6_frags_ctl_table);
503 return ip6_ctl_header == NULL ? -ENOMEM : 0;
504}
505
506static void ip6_frags_sysctl_unregister(void)
507{
508 unregister_net_sysctl_table(header: ip6_ctl_header);
509}
510#else
511static int ip6_frags_ns_sysctl_register(struct net *net)
512{
513 return 0;
514}
515
516static void ip6_frags_ns_sysctl_unregister(struct net *net)
517{
518}
519
520static int ip6_frags_sysctl_register(void)
521{
522 return 0;
523}
524
525static void ip6_frags_sysctl_unregister(void)
526{
527}
528#endif
529
530static int __net_init ipv6_frags_init_net(struct net *net)
531{
532 int res;
533
534 res = fqdir_init(fqdirp: &net->ipv6.fqdir, f: &ip6_frags, net);
535 if (res < 0)
536 return res;
537
538 net->ipv6.fqdir->high_thresh = IPV6_FRAG_HIGH_THRESH;
539 net->ipv6.fqdir->low_thresh = IPV6_FRAG_LOW_THRESH;
540 net->ipv6.fqdir->timeout = IPV6_FRAG_TIMEOUT;
541
542 res = ip6_frags_ns_sysctl_register(net);
543 if (res < 0)
544 fqdir_exit(fqdir: net->ipv6.fqdir);
545 return res;
546}
547
548static void __net_exit ipv6_frags_pre_exit_net(struct net *net)
549{
550 fqdir_pre_exit(fqdir: net->ipv6.fqdir);
551}
552
553static void __net_exit ipv6_frags_exit_net(struct net *net)
554{
555 ip6_frags_ns_sysctl_unregister(net);
556 fqdir_exit(fqdir: net->ipv6.fqdir);
557}
558
559static struct pernet_operations ip6_frags_ops = {
560 .init = ipv6_frags_init_net,
561 .pre_exit = ipv6_frags_pre_exit_net,
562 .exit = ipv6_frags_exit_net,
563};
564
565static const struct rhashtable_params ip6_rhash_params = {
566 .head_offset = offsetof(struct inet_frag_queue, node),
567 .hashfn = ip6frag_key_hashfn,
568 .obj_hashfn = ip6frag_obj_hashfn,
569 .obj_cmpfn = ip6frag_obj_cmpfn,
570 .automatic_shrinking = true,
571};
572
573int __init ipv6_frag_init(void)
574{
575 int ret;
576
577 ip6_frags.constructor = ip6frag_init;
578 ip6_frags.destructor = NULL;
579 ip6_frags.qsize = sizeof(struct frag_queue);
580 ip6_frags.frag_expire = ip6_frag_expire;
581 ip6_frags.frags_cache_name = ip6_frag_cache_name;
582 ip6_frags.rhash_params = ip6_rhash_params;
583 ret = inet_frags_init(&ip6_frags);
584 if (ret)
585 goto out;
586
587 ret = inet6_add_protocol(prot: &frag_protocol, IPPROTO_FRAGMENT);
588 if (ret)
589 goto err_protocol;
590
591 ret = ip6_frags_sysctl_register();
592 if (ret)
593 goto err_sysctl;
594
595 ret = register_pernet_subsys(&ip6_frags_ops);
596 if (ret)
597 goto err_pernet;
598
599out:
600 return ret;
601
602err_pernet:
603 ip6_frags_sysctl_unregister();
604err_sysctl:
605 inet6_del_protocol(prot: &frag_protocol, IPPROTO_FRAGMENT);
606err_protocol:
607 inet_frags_fini(&ip6_frags);
608 goto out;
609}
610
611void ipv6_frag_exit(void)
612{
613 ip6_frags_sysctl_unregister();
614 unregister_pernet_subsys(&ip6_frags_ops);
615 inet6_del_protocol(prot: &frag_protocol, IPPROTO_FRAGMENT);
616 inet_frags_fini(&ip6_frags);
617}
618